The field of the invention is cleaning of contact lenses by electrochemical or electrophoretic means. More particularly, contaminating deposits are removed from a contact lens by employing a small electrical current established through the lens that causes charged contaminating deposits, particularly protein contaminants, to migrate from the lens.
As is well known, contact lenses during wear become contaminated with deposits that adhere to the lenses over time. Proteins and lipids generated by the eyes' tear film, as well as microbial agents from the environment, adhere to the lenses such that they must be cleaned and disinfected frequently to preserve visual acuity and health of the wearer. Daily cleaners employing various surfactants are typically used to remove lipoid contaminants. The more difficult proteinaceous contaminants are removed by treating with enzyme. Disinfecting agents, such as hydrogen peroxide and other oxidants, are then utilized for disinfecting lenses, which agents often require reductants to neutralize residual oxidants before the lenses may be reinserted on the eye.
Typically, three separate regimens are involved in cleaning and disinfecting contact lenses in accord with the processes described above. It is well known that lens wearers do not always properly comply with lens care regimens, particularly where the regimen involves a number of components and steps. Thus, contact lens manufacturers and those concerned with lens care are always looking to simplify or combine lens care regimens.
One regimen or method which combines a number of cleaning and disinfecting steps utilizes electrophoretic techniques and apparatus. For example, Cowle et al in U.S. Pat. Nos. 4,732,185 and 4,921,544 describe a method for decontaminating and sterilizing a contact lens by electrophoresis wherein contact lenses, contained in a holder, are submerged in a buffer solution in which a unidirectional electrical field is established between two adjacent electrodes. Application of the unidirectional electrical field to the buffer solution results in the charging of protein and other contaminating materials on the lenses whereupon the charged contaminating materials migrate to an oppositely charged electrode. Since soft contact lenses are formed of a material having a matrix structure with pore sizes greater than the size of the typical contaminants, e.g. protein colloids, the contaminants are able to pass through the lens itself. Only relatively low voltage is required, for example, on the order of 9 volts DC at 200 milliamps.
A number of electrophoretic apparatus have been designed specifically for cleaning contact lenses. For example, Pankow in U.S. Pat. No. 5,227,039 describes a method and apparatus for cleaning and disinfecting contact lenses by electrokinetic means in which a pair of electrical transmission media members, formed of a pliant absorbent material and holding an electroconductive solution, receive a lens therebetween and help focus an electric current such that it cannot leak around the lenses. The current must flow through the lenses thus avoiding a disadvantage of other's apparatus such as the Cowle apparatus of U.S. Pat. No. '185. As a further advantage, the Pankow apparatus allows contaminants migrated from the lenses to be captured by the transmission media, thus preventing re-contamination of the cleaned lens.
A difficulty with these prior art methods and apparatus is that the apparatus must include a pair of electrodes and an electrical power source, such as a battery, for generating the required electrical field. The electrical field generating means adds considerable weight, bulk and complexity, as well as cost, to the known electrophoretic cleaning systems.
It would be an advantage to provide compositions and methods for cleaning and disinfecting contact lenses that eliminate the need for the conventional means or device for generating the required electrical field.